Make-up air heater



May 27, 1958 J. A. HARRISON MAKE-UP AIR HEATER 2 Sheets-Sheet 1 Filed July 27, 1956 J. A. HARRISON 2,836,409

y May 27, 1958 MAKE-UP AIR HEATER Filed July 27, 1956 2 Sheets-Sheet 2 mi A;

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f3? jaa Je 14C United States Patent MAKE-UP AIR HEATER James A. Harrison, Detroit, Mich.

Application July 27, 1956, Serial No. 600,470

8 Claims. (Cl. 263-19) This invention relates to a direct fuel-fired, such as a gas-fired, air heater and particularly to a heater for use with air blowers or fans which supply make-up air for shops and factories whose air is rapidly exhausted by paint spray booths, dust collectors, etc.

While my heater is particularly well suited for Warming make-up air and is hereinafter described in this conjunction, it is also well suited as an ordinary air heater to heat air recirculated within a building. l have shown the herein-described embodiment as a gas heater, but it will be understood by those skilled in the art that other fuels such as oil, kerosene, or the like might also be used.

In shops and factories having paint spray booths, dust collectors for grinders, and the like, or other equipment which'draws large quantities of air out of the Shop and blows it outside of the building, provision must be made for drawing fresh air into the building, and during winter months such fresh make-up air must be heated. In the embodiment of the invention herein disclosed, my heater is associated with a conventional blower or fan and warms the air directly by burning natural gas or the like in the air stream blown into the building.

Principal objects of my invention reside in the provision of a gas heater unit for air fans or blowers which is of simple and lightweight construction, may be manufactured at a low cost in proportion to the heating capacity, and which is highly efficient in operation from the standpoint ofomplete fuel combustion, transfer of heat to the fan or blower air stream, and forvthe volume of gas burned in relation to the size of the burner. The highly ellicient operation of the burner may in great part be attributed to the fact that a pressure drop is established through the whole burner assembly and this is combined with an injection effect by the gas jetted into the burner housing,

whereby a very substantial volume of fuel may be burned though the burner is of relatively small size.

Another object of the invention is the provision in an air, heater of an elongate straight venturi type burner housing having a pair of parallel walls coextensive with the burner housing and Haring apart along one edge to provide an air scoop with a plurality of partitions extendingtransversely between the walls and defining a plurality or" air passages opening at one end into the air scoop and opening into the opposite end through burner ports, and through which passages a portion of the air stream to be heatedv passes, with a gas manifold disposed in the air sc oroprat the intake ends of the passages to discharge gas thereinto, with the venturi shape of the burner housing and the injection eiect of the gas serving to create a high rate of gas and air flow through the passages.

Another object of the invention is the provision of an improved pilot grid at the discharge ends of the passages in the burner housing which serves to maintain a piloting of the gas and air mixture discharged from the passages by causing a portion of the mixture to eddy around the outletV ends of the passages with such eddying mixture supporting a piloting flame which pilots the remaining portion of the mixture discharging from the passages.

r"ice Still another object of the invention is the provision of a lightweight thin-walled burner housing which may be constructed of sheet metal and so designed as to be cooled by the air stream in which situated.

A still further object of the invention is the provision of an improved gas manifold assembly having an elongate tubular manifold provided with a plurality of longitudinally spaced-apart gas orifices through the wall thereof and with a gas inlet connection for the manifold and a piston in the manifold which is'shiftable longitudinally thereof between the inlet A,connection and the orifices to determine the number of orifices exposed to gas entering the manifold through the inlet connection, and with means connected to the piston to shift thesame in response to indications from athermostatic control device to vary the position of the piston and thereby vary the volume of gas discharging from the manifold in linear relationship to the position of the piston. Y

Another object of my invention' is the provisionV of a straight venturi type burner housing of the aforesaid char# acter in combination with the improved gas manifold associated together as a burner assembly which is dis posed within a heater shell transversely of the air ow through the shell and which shell is provided with orifice plate means for inducing an air pressure differential within the shell between opposite ends of the'burner assembly.

In general the invention includes a heater shell which is connected to one side `of a fan housing. A burner housing is disposed in the'heater shell to extend transversely of air flow therethrough. The burner housing is provided with a plurality `of -gas passages -extending transversely therethrough and opening at the downstream edge of the housing where the gas and air mixture passing through the passages burns. A pilot grid of novel design extends alongV the downstream edge of the housing and forms'burner ports at the discharge ends of the passages. The upstream edge of the housing is scoop shaped. A longitudinally extending perforated gas manifold is disposed along the upstream edge ofthe housing within the scoop and the perforations'of the manifold are directed toward'the passages to discharge gas thereinto. Within the manifold are one or more reciprocable pistons moving in response to an electric motor suitably connected to the pistons. A` gas inlet for the manifold is so disposed relative` to the travel of the pistons that as they move in one direction, fewer perforations or orifices of the'manifold are exposed to gas in the manifold, while with movement of the pistons in the opposite direction, 'a greater number of perforations are exposed, with the amount of gas discharging from/the manifold being determined by the number of exposed perforations.- The motor operates in response to a Vthermostatic control.

Other objects, advantages, and meritorious, vfeatures will more fully appear from the specification, claims, and accompanying drawings, wherein: -f f Fig. l is an end view of a make-up air heater of which my invention 'is a'part; Y Y

Fig. 2 is a front view of the assembly Y, shown in Fig. l; j Y Y i Fig. 3 is a fragmentary end Vview of my burner assembly including the burner housing and gas manifold;

Fig. 4 is a top view of the gas manifold taken substantially on the line 4--4 of Fig. l;

Fig. 5 is a cross sectional view taken on the line 5-5 of Fig. 4 through oneof the pistons in the manifold;

Fig. 6 is a cross sectional view taken on the line 6-6 of Fig. 3;

Fig. 7 is a cross sectional view taken on the line 7--7 of Fig. 6; Y`

Fig. 8 is a cross sectional viewvtaken on the line of Fig. 7; and

Fig.`9isV a schematic view of the thermostatie control for my heater. v Q

The make-up air heatershown in Figs. l and 2 comprises a gang-fan assembly '20 andmy improved heaterY unit per se 22 whichis connected between the `fan assemblyandiafduct 24 extending' outwardly through the Y t wall 26 Iofthe building in which the Vheater is disposed.

The air heater may be hung from the ceilingof the building Vor,y otherwise supported in any convenient fashion knot shown. Outside Vair is 'drawn by theY gang-fan assembly through the dnet24, through my heater unit 22,

Yassetto@ throughthe fans, and thereafter 'discharged into'the space within'thefbuilding through ports 28 in the fan housing; While Ymay heater Vis shown in Vconjunction withVV la gang-fan type blower, it is equally well suited for use withother types of blowers;

YThe. blower assembly includes a housing hayingY topandbottorn walls l30 and32, and end walls34and 36 connected` togetherin any suitable fashion with the Y front closed by a wall 38 through which fourports 28` open. Extending longitudinally vthrough thek length of',

the blower housing Vis a fan/or blower shaft 40 yupon which.are mounted inspaced relation four fans 42 for rotation `with shaft 40, YAn electric motor 44, mounted on thej blower housing, drives shaft ,40 by means of an endless belt Vconnection 45 yand pulley 46 mounted on shaft 40. This gang-fan assemly isof'conventional con housing. 'A motor-supporting bracket 521is connected in `any suitable fashion to one'of -the end 'walls of the heater unit'and an electric motor54 is mounted on and supported by the bracket as shown in'Figs. 1Y and 2.

Theheater unit22 .is interiorly providedwithr a pair of oricei plates 56 and' 58 which extendjacross the inner surface of .the walls of the. shelf,rand are connected theretoY in anyf suitable fashion, to provide a pressure drop `between the air inlet. and air outlet ends ofthe heater, shellf" 'Iheupper and lower shell'walls to which the oriceplatesf'are attached are indicated at 60 and Extending from one sidewall tothe opposite side Ywall lof .the heater shell substantially equidistant between g theupperandlower walls 60 and 62, and secured Yto the Y sideV walls in anycOnYenient fashion, VisV a burner housing generally indicatedinl Fig. Y1 at65 and shown more yparticularly inY Figs. 3 andV6-8.Y Disposedfin the air inlet end of the housing 64 is my improved gasmamfoldY assembly '66. The downstream end of housing 64 is disposed'just beyond the orificeplates 56 'and. 58 such that the downstream end of the housing 64 is ina lower pressure area than is` the upstream end. e The direction 4of air ow is eindicatedebyV the arrowfin" Fig. 1. 'Y Y Y Y TheV burner! housing Yis a linearly'extending structure vwhich may be formed of lightweight sheet lmetal and 'eomprisesfa-pairof 'spacedi'apart wallstS and 70 as shown particularlygin Fig'.V fwhicharelcoextensive*with the length of the housingf: The walls are heldin spacedapart parallel relation through substantially three-quarters of their widthr'by means of a plurality offpartitions v72 jwhich may beV provided at their uppery and Vlower Yedges with ears'74 that extend throughslots inlthefwalls 68 and 70 and are bent vover asshownY in Fig. `'7. vThe partitions 72 provide a plurality of gas and air passages extending transversely of the burner. housing throughout Athe length thereof and through which lgas "discharged Y fold.

` shell.

spaced-apart Yintervals with perforatons 1,04fth'roug'l1Y which gas within the manifold'rnayfescape. TheV perfora- Y s '4 by the gas manifoldY passes to the burner Vhousing.,VV Y

At the downstream end of the burner housingand extending along the discharge ends of the passages. is flame retention means in thefornr of a pilot grid 76. The primary function of the grid 76 is to elfect a piloting of the fuel discharging lfrorn the passages. It will be noted that the grid is disposed between the walls 68 and 701of the burner housing,v and is securedfthereto by bolts',

rivets, or the like V7 8, which extend through ears 79` of the grid. The grid is provided with a plurality of openings S9 therethrough which serve as burnerports. As shown in Figso-S, the inside surfaceV of the' grid around each port is beveled as at 82 and each port is aligned with one 'of the passages. The -bevels`82 terminate at the outside surface of the grid in a knife edge at 83,V withthe out. Y side surface of the grid being flat as at 84. The flat surfaces 84 around each port Y76 cooperate withr those marginal edge portions 68a and'70arofthe walls 68 and7tl.- to form eddy chambers at the lee side or downstream side of the grid. As the mixture of air and gas, flowing through the .passages leaves the ports 76, the mixture around the periphery of the lud stream swirls around behind the surfaces S4. VVWhen the mixture is lighted, `that portion of-the mixture swirling or eddyingbehind the surfaces 84 Yserves to Vpilot the principal'portion `of the mixtureissuingrfrom the ports, thereby sustaining the combustion of the gas. f, Y

At the upstream kend of the passagesin the lburner housing, the housingwalls 68 and 70 are apartas lat 913 and 92 and thereafter paralleleach otherY as at 94'and 96, and thereafter onceY again are apart as at Y98 and 160. This enlarged or flared upstream edge of Ythcburner housing'provides an air scoop and a` space withinVv which my improved gas manifoldassembly 66 is disposed.l The gas manifold assembly includes a linearly extending pipe or manifold per se'102 which is supported in lany jconvenientffashion' within the air scoop of theburner hous- 'Y ing. Therpipe i102Y or manifold per se may be mounted at opposite ends in the opposite Vend walls of the-heater The manifold A102 is provided at vlongitudinally tionsY 104V are directed-to dischargegas in the manifold fold into the passages through the VVburner housing.V The manifold may be provided with a gas inlet 106-into'which a gas line 10S-s connected to'supply'gas to the mani- Opposite ends of the manifoldY are closed by hollow plugs V'and 112. VWithin each plug isa bearing ,114 ,i

as shownfparticularly in Fig. 5 in connection'with plug 112. VA screw shaft 116 extends Vlongitudinally 'through' the manifold 102V with the Unthreaded end Y'portions of the screw received in the :bearings 114 which support the screw for rotation. The screw 116 is olset the axisfof the manifold 102 as shownin Figs. `4 and 5. The screw 116 is provided with right and left-hand threaded portions 118Aand 120.' The screw 116 extendsoutwardly of the manifoldfat vbothY ends thereof. y mounted, asl'shown in Fig.y 4, on the right-hand Vend (of the screw shaft, and a`collar 1,24, having a set screw 126, is received over the screw shaft 116 Ybetween the pulley and the bearingllZ. A similar collar Vis received over the opposite end ofthe screw shaft as at 128:Y The collars prevent Vlongitudinal shifting of screw shaft 116 within the manifold. Y

- Disposed within the manifoidfor longitudinal re'eipro-v cable movement are a pair of pistons 130 and 132. `Each piston, such as thepiston 132 shown in Fig. 5,.is pro vided with an annular O-ring receiving groove in which an-O-ring134is mounted. A felt lubricating sleeve 136 is .disposed about each pistonand held between a shoul'e y Yder 138 thereof and asnap ring 140.V The felt sleeve is soaked with a suitable lubricant which improves the slid` 'ing iit'of the 0-ring within the manifold, preventing wear Ythe downstream vend ofk i A pulley` 122 is Y b of the -ring and leakage of gas `by the pistons; Each piston is provided with an axially offset bore 142 therethrough and within the bore is disposed an internally threaded collar 144. The collar is threaded upon the screw shaft 116, and small screws or the like 146 threaded into the piston retain the collar 144 in the bore thereof. A suitable seal, such as an -ring 148, is disposed Within the bore 142 of each piston between cooperating shoulders 159 and 152 of the piston and collar respectively, and prevents leakage of gas between the collar and piston. The axial offset of the screw shaft and the offset of the bores in the piston serve to prevent rotation of the pistons upon rotation of the screw shaft.

The pistons 130 and 132 are shown in Fig. 4 in their outermost positions in the manifold such that gas entering the manifold through inlet 106 passes out of the manifold through all of the orifices 104 along the length of the manifold. When the pistons are disposed closer together, fewer orifices are exposed to the gas in the manifold and consequently a lesser volume of gas is discharged froin the manifold. The volume of gas discharging from the manifold varies in a linear relation to the position of the pistons in the manifold. Because of this, a simple control device for the movement and positioning of the pistons may be provided. A thermostatic control device 154 is provided as generally shown in Fig. 9 which is of conventional construction and therefore will not be described in detail. The thermostatic control includes a bulb 156 which may be disposed either in the space to be heated by the heater or in the air stream of the heater outlet. The bulb is connected by a tube 157 to a temperature controller 158 which is responsive to the fluid pressure within the bulb 156 and tube 157 to energize a reversing relay 16d which controls the direction of rotation of the shaftV 162 of motor 42. The temperature controller S may be set to energize l the reversing relay to reverse the direction of rotation of the motor shaft when the temperature of the air surrounding bulb 156 rises or falls beyond predetermined limits. Upon rotation of shaft 162 of the motor 42 in one direction, the pistons 130 and 132 are moved toward each other, while rotation of motor shaft 162 in the opposite direction will move the pistons away from each other. lt is therefore apparent that the volume of gas discharged from the manifold is in direct relation to the amount of rotation of the screw 116 and consequently the rotation of the shaft 162 of the motor 42. Because of this, a simple type of control of the volume of gas discharging into the burner housing is effected.

The high efhciency of my heater unit is due in substantial part to the fact that the burner housing is, as shown in Fig. 6, a straight venturi and is disposed in the heater shell such that opposite edges of the housing are in high and low-pressure areas and the pressure drop occurs across the whole burner housing both interiorly and exteriorly thereof. This pressure drop is accompanied by an injection eiect of the gas being blown from the manifold into the passages. The com` bination injection effect and pressure drop across the burner housing promotes the ow of a very substantial amount of gas through the housing to be burned at the burner ports thereof though the housing is not of large size.

assegna 92 and its speed' increasessubstantiallylas it passesv into passages between walls 68 and 70. This speed is also increased, as mentioned above, by the injection effect of the gas blowing out of orifices 104.

What I claim is:

l. A heater assembly for an air fan comprising, in combination: a heater shell for connection to one side of the fan, a burner housing within the shell extending transversely thereof and provided with a plurality of passages opening at opposite ends upstream and downstream of the air ilow through the shell with the downstream ends in a lower pressure area than the upstream ends, said burner housing adjacent the upstream ends of the passages haring outwardly to provide an air scoop, a fuel manifold extending along the upstream ends of the passages within the air scoop and provided with a plurality of fuel outlets spaced apart along the length of the manifold for discharging fuel into said passages, a fuel inlet connection for the manifold, means sealingly disposed in the manifold and shiftable therethrough between the inlet connection and said fuel outlets to vary the number of outlets exposed to fuel discharging into' the manifold from the inlet connection, and other means including a thermostatic control connected Vto the first-mentioned means for shifting the same in response to temperature indications from the thermostatic control.

2. A heater assembly for an air fan comprising, in combination: a heater shell for connection to one side of the fan, means within the shell establishing an ori`v fice through which air passes in moving through the Shell to establish an air pressure diierential within the shell, a burner housing within the shell extending transversely thereof and provided with a plurality of passages opening at opposite ends upstream and downstream of the air flow with the downstream ends of the passages in a lower pressure area than the upstream ends, a fuel manifold extending along the upstream ends of the passages and provided with fuel outlets for discharging fuel into the passages, a fuel inlet connection for the manifold, and means for controlling the volume of fuel discharging from the manifold into said passages.

3. A heater assembly for an air fan comprising, in combination: a heater shell for connection to one side of the fan, means within the shell establishing an orifice through which air passes in moving through the shell to establish an air pressure differential within the shell, a burner housing within the shell extending trans- Because the burner housing is disposed within the air stream at the suction side of the fan, the housing may be made of thin and/or lightweight sheet metal such as aluminum, and the air stream passing around and through the burner housing effects a cooling thereof.

The air spaces 164 and 166 shown in Fig. 6 around the gas manifold and between the manifold and the flaring walls 90 and 92 of the housing are of greater cross section than the air passages between walls 68 and 70 and therefore there is no slowing down of air as it passes around the gas manifold. The air passing around the gas manifold is compressed by the walls 90 and versely thereof and provided with a plurality of passages opening at opposite ends upstream and downstream of the air ow with the downstream ends in a lower pressure area than the upstream ends, said burner housing at the downstream ends of said passages provided with a piloting grid through which a mixture of air and fuel discharging from said passages passes with the grid provided with a wall portion surrounding each passage opening and around which wall portion the air and fuel mixture eddies in discharging from the passages.

4. A heater assembly for an airfan` comprising, in combination: a heater shell for connection to one side of the fan, means within the shell establishing an orifice through which air passes in moving through the shell to establish an air pressure diierential within the shell, a burner housing within the shell extending transversely thereof and provided with a plurality of passages opening at opposite ends upstream and downstream of the air ow with the downstream ends in a lower pressure area than the upstream ends, said burner housing adjacent the upstream ends of said passages aring outwardly to provide an air scoop, a fuel manifold extending along the upstream ends of the passages and disposed in the air scoop and provided with fuel outlets for discharging fuel into the passages, a fuel inlet connection for the manifold, and means for controlling 'i t the -vo ume .of fuel discharging fromthe manifold into s said passages.

Y 5. vAV gas burner for anairfancomprising: `Vafilieater shell for connection to enel-side of the fan, a Vburner housing disposed within the shell and provided with a Y Y plurality of fuel and air passages openingat opposite end'sjupstream and downstream'of air iiow through the shell, a fuel manifold extending along adjacent the upstream ends of the passages and provided with longitudinally spaced-apart perforations for discharging V,fuel into'the passages, aV fuel inlet for the manifold, and a piston reciprocable in the manifold between the inlet andY the perforations'to admit fuel to those perforations lying b'etweenthe piston and fuel inlet, and means` for reciprocating Vthe piston to a variety kof @positions longitudinally of thermanifold'to Vvaryrrthe volume of fuel discharging therefrom. Y

i 6. A gash'urner Comprisingz" .an elongate burner housp ing'h'a'vingza pair of parallel, spaced-apart walls coextensive YwithV 'the lengthof the housing and held in spacedapart relationby a plurality of partitions extending trans-r versely between the walls and spaced apart longitudinally therealo'ng, said walls and partitionsV defining 'fuel' and air passages opening at opposite ends toward opposite lateral Y edges of the wall'sjpajfuel manifold extending along one walls coextensive'with the length-ofthe housing `and flaring 'apart along Vone longitudinal edge to provide an K ,y air scoop for ycatching'and passing lair transverselygbe? Y tween saidrwalls, a plurality of partitions extending trans` versely of said structure between lthe walls and vspaced v apart longitudinally VtherealongVV and defining passages through which air ventering the scoop passes to discharge at the opposite longitudinal edge of the structure, a Ypilot grid extending along the discharge ends of said Vpassages and connected to said structure and provided with burner Y ports aligned with the passages, said V`gridraround each of the ports provided `with'a wall portion having a flat Vsurface surrounding the opening and behind which surface aV fuel and air mixture eddies in discharging .from the aligned passage. Y y

8. A heater assemblyffor an airfan comprising,V in combination: an enclosure through which the fan creates a draft, a burner housing Within the l enclosure Vextending transversely thereof and provided with Va pluralityrof passages '.oprening at opposite ends upstream and downstream of the air iiow through Vthe enclosure with the Vclownstrearn endsin a lower pressure area than the upstream ends, .said burner Vhousing adjacent the upstream ends of the passages flaring outwardly to provideV an air scoop, a fuelimanifold `extending along the upstream ends of the passages within the air scoop and provided with Va plu- VVrality of fuel outlets spaced apart along the length of the manifold for discharging fuel into said passages, and a fuel inlet connection for the manifold. *i Y Y References Cited in the le of this patent UNITED STATES PATENTS 2,228,114 Hess Jan. 7, 1941 Browne Mar. 9, 179126 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Pawel. um eeamiee May 27, 195e James A Harrison It is hereby eertijied inap error appears in the above numcered paient requiring correction and thai; ine said Letters Paien': should read as corree'ted loelow ln the drawings Sheet, lg Figu 2q delete the numeral 162 zeeompanying lead lineV applied to 'line snat oi upper motor f au te the outer end oi line sha-ft oi lower motor 5l) apply the 162,1 and to drive peli; between the motor shait 162 elle pulley above, apply *elle numeral 163E In Sheet- 2 o the drawings.1 Fig 8v the numeral "84H as applied izo the ear oi the grid at ne lei of that figures should vloe m 79 #-1 In Sueet oi the drawings(t Fig!u 9v the numeral W12" should loe 54 -e in the printed speeiiieationV Column 3g lines 56V 57 and 59M, for "64", each occurrenceE read W 65 mg column 5q 55 for "42" read 54 same line 35 after "oi molor 42" insert ine sentence Shat 162 is connected by an enelD less drive belt or the like 163 ico pulley 122 on screw snail@ 116a same column 5q lines AO and 47V for 42"v each occ-ure rence,I read 54 Signec and sealed this 3rd day of January 1961o (SEAL) Atest:

KARL 1-1, AXLINE ROBERT Co WATSON Attesting Officer Commissioner of Patents 

